I don't know if that is the only way, but it worked. I added a .DOC and chose the option "Let Windows choose and run appropriate application". It started right up. I did not have to do that for the .PDF attachments. Thanks for you assistance.

I am using the latest pmail on a Windows 8 os. I installed MS Office 2013. I am not able to open a WORD document attachment from pmail. Any suggestions?

You can define content viewers in Tools > Options > Incoming mail > Content viewers.

One thing to be aware of.  If you have attachment preview enabled it can interfere with the opening of an attachment via a double click.